Traditionally, for the lifting of containers an especially just for that purpose designed loading means called spreader is used. The spreader engages with the lifting holes situated on the corners of the container with its locking units called twistlocks. The apparatus is used in connection with different forklift trucks and reach trucks moving on wheels, and cable cranes.
During the operation fairly hard impact stresses are directed towards the spreader and therefore the whole operation has to be stopped very often for repairing or changing of the whole apparatus.
Another problem is to be able to aim the twistlocks at the lifting holes on the corners of the container due to the manufacturing tolerances of containers and damages during a transport.
In order to be able to engage the twistlocks reliably it is essential to recognize the distance of the container from the twistlock so that all the twistlocks are simultaneously in the correct place. Recognizing limit switches are damaged fairly easily because accelerations are extremely high.
Also distortions of moving rods or levers can easily cause malfunctions. In those cases also counter surfaces on the supporting structure can be damaged and the whole structure has to be repaired or changed.
Prior-art technology in the field of the invention is represented for example by the patents GB2294027 and EP0442154. In these publications different types of absorption solutions and levers for recognizing the corners of the container are presented. In both cases the concentration is directed mainly at the absorption of the axial force, and as to the guidance of the twistlock, at the swing in relation to the self-aligning bearing.
Swedish patent publication SE 339740 shows a twistlock arrangement where moving parts are situated inside a closed space, and where the coupling for transmitting the torque does not move in the vertical direction. A disadvantage of the solution presented by the Swedish patent publication is the fact that it is complicated of its structure and that receiving of the horizontal forces is fairly poor.